For the purpose of various tasks—e.g. inspection, cleaning de-rusting, decontamination of radioactivity and repairs—in hard to access locations, such as high walls, ceilings, chimneys, the inside of pipes or tanks and other closed spaces, ships or airplane surfaces, etc., it is known in the art to utilize automatic working devices that may be operated by remote control to avoid human presence at the often dangerous location. Examples of such automatic working devices are vacuum wall crawlers, that may bring a tool or camera or the like in close proximity to a vertical, inverted, inclined surface, curved, compound, or tapered surface and to move the tool to various locations on the surface. Some common scenarios include inspecting, cleaning, de-painting, or otherwise maintaining the surfaces of airplanes, submarines, storage tanks, high rise buildings, and other similar structures. These surfaces can be inconvenient, difficult or even dangerous, for people to access directly. The difficulty can be increased when these surfaces are curved, compound, or tapered.
U.S. Pat. No. 7,404,464 describes a traction device for moving on an inclined working surface by applying suction force. The traction device has an upper plate for connection to a wall crawler, and a belt in the form of a thin band formed in a flexible material, the band having a plurality of openings through the belt for suction to a surface, the belt having an outer surface with a high coefficient of friction for movement on coarse surfaces, and an inner surface with a low coefficient of friction for easy sliding over a manifold plate. Further, it discloses a toothed belt for driving a roller of the traction device engagement means.
U.S. Pat. No. 4,664,212 discloses a vacuum wall crawling device, comprising two belts formed as thin bands in a flexible material and each having an inner surface and an outer surface with a plurality of holes through the belt. The inner surface of the bands contacts a stainless steel plate having a small friction coefficient, the plate being attached to a support beam, the plate allowing smooth sliding between belts. The wall crawling device is driven by chains between a motor and a pulley.
The devices disclosed in U.S. Pat. No. 4,664,212 and U.S. Pat. No. 7,404,464, both have means provided to distribute vacuum to recesses in the suction tracks of the device, and both discloses relatively thin suction tracks. If the devices needs to move on a surface having obstacles e.g. protrusions or on curved surfaces the documents teach to section the means provided to distribute vacuum into units being hinged/articulated relative to each other in a frame to compensate the force acting on the portion of the suction tracks between rollers carrying the suction tracks. In U.S. Pat. No. 4,664,212 this is done by making slits in the means provided to distribute vacuum. Therefore, the internal means for distributing vacuum in the two devices are intricate mechanisms, which are heavier, and more complicated and expensive to manufacture.